Isner barely held off a tenacious Levine, who is ranked No. 133 in the world and needed a wild-card entry into the main draw.

Levine, who lives nearby in Boca Raton, trailed the 11th-ranked Isner throughout the tiebreaker. The match ended when Levine's backhand hit the top of the net and carried long, putting Isner into the second round.

Fourth seed Andy Roddick, making his first visit to the Delray Beach tournament since 2003, plays his opening match against Philipp Petzschner of Germany on Tuesday night.

Isner, playing against his fourth straight left-hander, won on his sixth match point - all on Levine's serve. Levine had five set points in the second set.

"I served very well and to be honest I was very lucky to win it,'' said Isner, who had 13 aces. "To be honest, if I lost that second set I didn't really fancy my chances in the third because the humidity was getting to me.

"I was very lucky to advance.''

Isner is 9-1 in tiebreakers this year, with the lone loss coming in the quarterfinals to eventual champion Jurgen Melzer in Memphis last week.

The second set marked the longest tiebreaker Isner has ever played. He won a second-set tiebreaker 16-14 over Victor Hanescu in the first round of the 2009 U.S. Open.

Levine has been working on improving his ranking on the Challenger circuit. His last ATP World Tour win was against American Ryan Harrison in the first round of the June 2010 Queen's Club tournament.

Nieminen has already won a title this year at Sydney, while Cilic was playing his first match of the season. The 21st-ranked Cilic has been nursing a left knee injury and this was his first match since last November.

Known for a big serve, Cilic racked up nine aces - but he was streaky. His first-serve percentage was only 48 percent.

"It was my first match for a while and it felt a little bit awkward I would say,'' Cilic said. "I played some moments pretty good but I think my fitness level, not great. ... I expected that to happen.''